Lens edging machine for fitting spectacle lenses

ABSTRACT

A lightweight edge grinding machine having a grooved grinding wheel receiving the edge of a lens supported upon a pivoted head. A fluid-actuated cylinder and piston unit pivots the head toward and away from the wheel. A lens is adjusted to fit the wire rim of a spectacle frame by trying it for size, estimating the duration of additional edge grinding necessary, setting this duration on an automatic timing device of the lightweight edge grinding machine, inserting the lens in the machine and starting the operation. The machine stops automatically when the requisite amount of grinding has been effected.

United States Patent Raphael 1 Aug. 7, 11973 [54] LENS EDGING MACHINE FOR FITTING 3,315,415 4/1967 Lannom 51/97 R SPECTACLE LENSES FOREIGN PATENTS 0R APPLlCATlONS [76] Inventor: Osmond Philip Raphael, 52, 808,329 2/1959 Great Britain 51/101 LG Clarewood Ct., Seymour PL, London, England Primary Examiner-Donald G. Kelly [22] Filed: July 21, 1971 Attorney-Watson et al.

[21] Appl. No.: 164,795 [57] ABSTRACT A lightweight edge grinding machine having a grooved [30] Foreign Application Priority Data grinding wheel receiving the edge of a lens supported upon a pivoted head. A fluid-actuated cylinder and pis- July 22, 1970 Great Britain 35,444/70 ton unit pivots the head toward and y from the 52 us. c1. 51/91 R, 51/105 1.0, 51/284 wheel [51] Int. Cl. B241! 9/14 A lens is adjusted to fit the of a Spectacle 581 Field of Search 51/97 R, 101 LG, frame y y g it for Size, estimating the duration of 51/105 R, 105 G 234 additional edge grinding necessary, setting this duration on an automatic timing device of the 56 References Cited lightweight edge grinding machine, inserting the lens in UNITED STATES PATENTS the machine and starting the operation. The machine 3 520 09] 7,1970 Raphael 5] LG X stops automatically when the requisite amount of 3:513:598 5/1970 Asselini: 1:11.... 51/101 LG gmdmg has effected 2,247,228 6/1941 Flygare 51/97 R UX 4 Claims, 5 Drawing Figures l l /)g LENS EDGING MACHINE FOR FITTING SPECTACLE LENSES This invention relates to a machine for fitting spectacle lenses to wire-rimmed spectacle frames.

Wire spectacle rims are practically non-stretchable and cannot be sprung onto the lenses. It is therefore the practice to split the rims and provide lugs at the wire ends which can be drawn together by a screw to tighten the rim round the lens. Ideally, the peripheral length of the lens should be such that when the screw is tightened there is no gap between the lugs and the lens is not loose in the rim. It is the normal practice to grind the lens to almost the final size and shape, with a bevelled edge, on a template-guided edge grinding machine. A skilled operator then adjusts the lens tothe required final size by lightly applying the edge of the lens, by hand, against a grinding wheel until, by trial and error, the correct amount of glass has been ground away and the lens is a proper fit in the rim. This is a timeconsuming operation requiring considerable skill and experience.

It is an object of the invention to provide a machine for performing this adjustment operation more effi' ciently.

According to one aspect of the present invention the machine may be utilized in fitting a lens to the wire rim of a spectacle frame by trying the lens in the rim, estimating the amount of adjustment required, placing the lens in the edge grinding machine provided with a presettable automatic stopping device, pre-setting the device to stop the edge grinding operation when the estimated amount of adjustment has been effected, starting the machine, removing the lens therefrom when the edge grinding operation has stopped and placing the adjusted lens in the rim.

The invention is based on the appreciation that with only a little practice an operator can estimate accurately the setting necessary to produce the required degree of adjustment. This is remarkable because the setting depends not only on the gap observed between the ends of the wire rim when the lens is tried, but also on other factors such as the size, shape and thickness of the lens. Nevertheless, it has been found that operators can assess these various factors and obtain satisfactory results with much less experience than is needed for conventional hand fitting.

The automatic stopping device can be arranged to operate in dependence on any factor which determines the amount of glass ground away. The most convenient is for the device to be time-dependent. In this case the device can be a pre-settable timing device which begins to operate when the machine is started and automatically stops the edge grinding operation when the preset time interval has elapsed. Thus, when trying the lens in the rim the operator estimates the duration of the edge grinding operation necessary to adjust the lens, sets the timer accordingly, and then inserts the lens in the machine and starts the edge grinding operation.

According to another aspect of the invention a machine for adjusting a lens to fit the wire rim of a spectacle frame comprises a rotatable grinding wheel having a circumferential groove to receive the edge of the lens, a lens-supporting head pivotally mounted for movement towards and away from the grinding wheel, means for'retaining and rotating the lens in the head such that the edge of the lens is presented to the grooved grinding wheel and the lens is rotated about an axis substantially parallel to the axis of rotation of the grinding wheel, means for pivoting the head in the direction away from the grinding wheel and a pre-settable automatic device for actuating the means for pivoting the head.

The head is preferably of lightweight construction, i.e. made as light as possible consistent with adequate strength and rigidity, so that the lens is only lightly pressed against the grinding wheel. Owing to the light pressure only a very small amount of glass is removed on each revolution of the lens and template guidance is unnecessary, the edge of the lens itself providing sufficient guidance.

Preferably, the cross-section of the groove in the grinding wheel is the complement of the cross-section of the bevel of the lens edge so that this grinding operation takes place uniformly along the whole of the flanks of the bevel.

The lens may be held in the machine between pads at the inner ends of coaxial rotatable shafts in the head, one of these shafts being axially movable so that lenses can easily be inserted and removed. The shafts are slowly rotated when the machine is operating so that the lens is rotated and continuously presents a different segment of its periphery to the rotating grinding wheel. For example, the shafts may rotate at 4' revolutions per minute, the lens making a complete revolution every 15 seconds.

At the end of the selected time period the timing device automatically terminates the edge-grinding operation by actuating the means for pivoting the head to lift the lens clear of the grinding wheel. It may also actuate a switch in the circuit of an electric motor which rotates the lens, to stop the lens rotation.

As the amount of glass removed at each revolution is so small, it is not necessary that the lens should always perform a whole number of revolutions. In other words, the timer need not be pre-set to an exact multiple of 15 seconds.

The invention may be constructed in various ways, and a specific embodiment will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of an edge grinding machine embodying the invention;

FIG. 2 is a side view looking in the direction of the arrow II in FIG. 1;

FIG. 3 is an enlarged fragmentary view of the grinding wheel and lens;

FIG. 4 is a view of a lens being tried in a wire rim of a spectacle frame; and

FIG. 5 is a circuit diagram.

The lens 141 has already been ground in a conventional template-guided edge grinding machine which grinds the lens to approximately the desired profile as determined by the shape of the template. That machine also grinds a bevel of about included angle at the edge of the lens as best seen in FIG. 3.

The lens M is to be fitted into the wire rim 45 of a spectacle frame (see FIG. 4). As a first step the opera tor tries the lens in the frame and observes the size of the gap'4i6 between the lugs 51 and 52 which later are to receive a screw 53 for securing the wire rim 45 around the adjusted leris. With a perfect fit, the gap 46 should be virtually non-existent, with the lens firmly gripped in the rim. From the size of the gap in the trial fitting, the operator estimates the setting of an automatic timing device 60 necessary almost to eliminate the gap. He then inserts the lens in the machine shown in FIGS. 1 and 2 for adjusting the lens to size by grinding away the requisite amount of glass from the edge of the lens.

Referring to FIGS. 1 and 2, the machine comprises a lens mounting head which is of lightweight construction of generally H shape configuration in plan. It is pivoted on a horizontal shaft 11 so as to be movable up and down in the direction of the arrow A in FIG. 2. The horizontal shaft 11 is supported in a yoke 12 which is pivotally mounted on a vertical post 13 so that the head 10 can also swing laterally in the direction of the arrow B in FIG. 1.

The lens 14 is clamped between two pads 16 and 17 in the front of the head 10. The pad 16 is mounted on the inner end of a shaft 18 which is journalled in a portion 19 of the head so as to be rotatable therein but not movable axially. The other pad 17 is mounted on a shaft 20 which is journalled in a formation 21 of the head so as to be rotatable therein together with an outer tubular shaft 22, and to be movable axially. The pad 17 and its shaft 20 are urged to the left in FIG. 1 by means of a light coil spring 23, and can be withdrawn towards the right in FIG. 1 to release the lens 14 by pulling a knob 24 attached to the end of the shaft 20.

The shaft 11 is rotatable and at its left hand end in FIG. 1 is connected by means of universal joints 25 and 26 and a somewhat flexible shaft 27 to reduction gearing 28 associated with an electric motor 29. During operation of the machine the motor 29 rotates the shaft 11 slowly at a uniform speed, e.g. 4 revolutions per minute, the transmission shaft arrangement 25, 26, 27 permitting lateral movements of the head 10 in the direction of the arrow B.

Fixed to the shaft 11 at each side of the head 10 are sprockets 30 and 31. Corresponding sprockets 32 and 33 are fixed to the shafts l8 and 22 respectively. Pivotally mounted on the shaft 11 are arms 34 and 35 which carry at their forward ends idler sprockets 36 and 37. A chain 38 connects the sprockets 30 and 32, the upper run of the chain being tensioned by the idler sprocket 36, while another chain 39 connects the sprockets 31 and 33, the upper run of this chain being tensioned by the idler sprocket 37. Thus the slow rotation of the shaft 11 produces corresponding slow rotation of the shafts 18 and 20 and of the lens 14 clamped between the pads 16 and 17. Below the front of the head 10 there is a grinding wheel 40 the shaft of which is supported in bearing blocks 41. This shaft 42 carries a belt pulley 43 which is connected by a belt 44 and a corresponding pulley to an electric motor (not shown in FIGS. 1 and 2 but shown at 73 in FIG. 5) which rotates the grinding wheel 40 at high speed.

As shown in FIG. 3 the grinding wheel 40 has a circumferential V-section groove having an included angle of 120", corresponding to the bevel 15 already ground on the edge of the lens 14.

Extending rearwardly from the head 10 is a rod 47,

and pivotally attached thereto is a vertical rod 48 carry-- ing at its lower end a disc 49. This disc is immersed in a viscous liquid in a container 50. These parts constitute a damping device whereby any tendency to rapid vertical vibration of the head 10 will be resisted by the viscosity of the liquid whereas slow movements such as are produced by the slow rotation of the non-circular lens 14 are not appreciably resisted.

Mounted on the fixed base 55 of the machine (FIG. 2) is a pneumatic cylinder and piston unit 56 which constitute means for pivoting the head 10 upwards to lift the lens 14 clear of the grinding wheel 40 at the end of the period pre-set by the operator on the automatic timer 60. Leading to the lower end of the cylinder of the unit 56, below the spring-loaded piston 57 therein, is a compressed air line 58 extending from a twoposition change-over valve 59. The change-over valve 59 in a first position connects the line 58 to a passage 61 open to the atmosphere so that piston 57 is at the bottom of the cylinder of the unit 56 to allow the head 10 to rise and fall freely as the lens 14 is slowly rotated in contact with the grinding wheel 40. The change-over valve 59 in a second position blocks the passage 61 and connects the line 58 to a line 62 leading from a supply of compressed air. When the valve is in this second position the pressure of the compressed air admitted to the cylinder raises the piston 57 therein and so pivots the head 10 upwards to lift the lens 14 clear of the grinding wheel 40. The valve 59 is actuated by a solenoid 63. When it is not energised, this solenoid allows the valve 59 to occupy the first position, and moves the valve to the second position only when it is energised. One function of the timer 60 is to energise the solenoid 63 at the end of the period pre-set by the operator. The timer 60 has a dial 64 on which the operator sets the period which he judges to be appropriate for providing the requisite amount of additional grinding of the lens 14.

Referring to the circuit diagram in FIG. 5, there is shown a main switch connected to a mains supply 71. Closure of the contacts of the main switch allows electric current to pass through lines 72 to the electric motor 73 which drives the grinding wheel 40, and also through lines 74 to the automatic timing device 60. In the timing device there is a change-over switch having a movable contact 75 which in a first position touches a fixed contact 76 and in a second position as shown touches another fixed contact 77. The movable contact is permanently connected to one of the lines 74. In the first position, current flows via the contacts 75 and 76 through a synchronous timer motor 78. In this first position, current also flows through lines 84 to the lens rotating motor 29. Thus, closure of the main switch 71 starts the timing operation and starts the slow rotation of the lens 14. The synchronous motor 78 begins to move a contact arm 79 from a zero time position towards another contact 80, the position of which in the path swept by the contact arm 79, and hence the period of time which elapses before the contact arm 79 touches the contact 80, is adjustable by the operator on the dial 64. The contact 80 is connected to a solenoid coil 81, and when the arm 79 touches the contact 80 a circuit is completed across the lines 74 so that the coil 81 is energised. This moves the movable contact 75 from the first position to the second position as shown. This breaks the circuit through the timer motor 78 and through the lens rotating motor 29, and makes a circuit via the fixed switch contact 77 through lines 82 and the solenoid 63 of the changeover valve 59 so that the head 10 is lifted, to terminate the adjusting operation. A holding solenoid coil 83 is also energised to hold the switch contact 75 in the second position after the circuit via the fixed contact 76 has been broken. When the operator opens the main switch 71, the movable contact springs back to its first position. The movable switch arm 79 is returned to its zero time position and the machine is ready for the use with the next lens.

The same machine can also be used for another purpose, namely for the finishing edge grinding of lenses as described in US. Pat. No. 3,520,091 to Raphael, issued July 14, 1970. For that purpose the machine may be provided with an alternative grinding wheel with a groove having a smaller included angle, as described in that patent specification. Also, in addition to the adjustable timer 60, such a dual purpose machine could have an automatic switch which stops the grinding operation when the lens has made one complete revolution. This is not essential because the machine can be caused to stop on the completion of a single revolution of the lens by setting the timer at the appropriate time for one revolution, e.g. seconds.

What I claim as my invention and desire to secure by Letters Patent is:

l. A machine for adjusting a spectacle lens to fit the wire rim of a spectacle frame, comprising a grinding wheel having a circumferential groove to receive the edge of said lens, means to rotate said grinding wheel,

a lens-supporting head, pivot means supporting said head for movement toward and away from said grinding wheel, means for holding said lens in said head with said edge of said lens presented to said grooved grinding wheel and with the axis of lens rotation substantially parallel to the axis of rotation of said grinding wheel, means comprising a fluid-actuated cylinder and piston unit for pivoting said head in the direction away from said grinding wheel, a valve to admit fluid to said cylinder and piston unit, and a pre-settable automatic device for actuating said valve.

2. A machine according to claim 1 in which said presettable automatic device is a pre-settable timing desaid head is not required. 

1. A Machine for adjusting a spectacle lens to fit the wire rim of a spectacle frame, comprising a grinding wheel having a circumferential groove to receive the edge of said lens, means to rotate said grinding wheel, a lens-supporting head, pivot means supporting said head for movement toward and away from said grinding wheel, means for holding said lens in said head with said edge of said lens presented to said grooved grinding wheel and with the axis of lens rotation substantially parallel to the axis of rotation of said grinding wheel, means comprising a fluid-actuated cylinder and piston unit for pivoting said head in the direction away from said grinding wheel, a valve to admit fluid to said cylinder and piston unit, and a pre-settable automatic device for actuating said valve.
 2. A machine according to claim 1 in which said pre-settable automatic device is a pre-settable timing device.
 3. A machine according to claim 1 in which said pre-settable automatic device is effective also to stop said means for rotating said lens at the end of the pre-set duration.
 4. A machine according to claim 1 wherein the edge of said lens is received within the groove of said grinding wheel solely by means of the weight of said head, whereby any other means for guiding said movement of said head is not required. 